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Trib Ology Roller

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    Lubrication

    Of

    Roller Bearings

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    Roller Bearings have a long history

    around 700 BC

    1794

    186940 AC

    around

    3000 BC

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    Tasks of Roller Bearings

    lreducing fr ict ion

    ltransfer o f loads

    lguiding rotat ing parts

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    Friction

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    Energy losses through friction

    10 % = 1/2 E [AUS+BR+E+S]

    Although rolling friction is already very low, manufacturers of roller

    bearings and lubricants work continuously on further improvements..

    SKFone of the worlds biggest manufacturers of roller

    bearings

    made the following calculation:

    If it can be managed to drop the friction in all roller bearings

    installed on the globe only by further 10%,

    the combined total electricity consumption of the countries

    Australia, Brasil, Spain und Sweden

    could be cut to a half !

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    Roller Bearings are named after theShape of their rolling Elements

    ball spherical roller

    symmetrical

    spherical roller

    asymmetrical

    cylindrical roller

    needle roller

    conical roller

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    Friction in Roller Bearings

    lsm all por t ion of ro l l ing fr ic t ion

    lbu t con siderable share of sl id ing fr ict io n at:

    roller bearing rings

    cages and / or

    rolling elements against each other

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    Kinds of Lubricationof Roller Bearings

    9,5% by oi ls 0,5% by sol id lubr icants o nly

    90% b y greases

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    DN- Factors for OKS Bearing Greases

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    Temperature Range of OKS BearingGreases

    with MoS2

    with MoS2+ Mox- Active

    with MoS2

    with Mox- Active

    with MoS2+ Mox- Active

    with PTFE

    with PTFE

    with white solid lubricants

    with PTFE

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    Lubrication by greases

    Grease pump

    Contamination may

    cause bearing failures.

    Seals protect to a large

    extent from outside contaminations.Frequent relubrication is required when

    the hazard of grease contamination exists.Same applies if the grease should seal also

    against penetrating moisture.

    Contamination penetrating through

    labyrinth channels.

    Newly supplied grease pushes out both

    used up and contaminated grease

    through the labyrinth packing seals.

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    Relubrication Intervals for Greaselubricated Roller Bearings

    Small bear ings with lateral seals or co ver plates do not

    need any relubr ication . They are already for - l i fe lubric ated.

    For al l other rol ler bear ing s relubr icat ion intervals become val id.

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    Guidelines forRelubrication Intervalls

    10 000

    6 000

    4 000

    3 000

    2 000

    1 500

    1 000

    500

    300

    200

    150

    100

    50

    20 000

    15 000

    10 000

    7 500

    5 000

    2 500

    1 500

    1 000

    750

    500

    250

    20 000

    15 000

    10 000

    5 000

    3 000

    2 000

    1 500

    1 000

    500

    100 200 500 1 000 2 000 5 000 10 000n [U/min]

    tfa

    tfb

    tfc

    Lub ricat ion interval ,g iven by serv ice hours

    tfa= radial ball bearing

    tfb= cylindrical roller bearing / needle bearing

    tfc= self alignin g roller bearing / taper roll ing bearing / axial roller bearing

    massive cylin drical roller bearing (0,2 tfc), ax ia l cy li nd ri ca l ro ll er

    bearing (0,5 tfc)

    500 420 360 280 240 200 160 120 100 80 60

    40

    20

    d=10

    Example: A deep-groove ball bearing with an internal diameter

    d= 100mm running at a speed of n = 1000 rpm. The operating

    temperature lies between 60 and 70 C.

    Which is the expected relubrication interval?

    The vertical in point n= 1000 rpm on the abscissacuts the curve for d= 100mm. From there the horizontal leads

    to the outer left-hand scale (deep- groove ball bearings)

    indicating a relubrication interval of 10000 service hours

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    Correction of Relubrication Intervals

    The assessed intervals are valid only for:

    lbear ings in s tat ionary machines

    lno rmal load

    lageing-proofed g reases

    ltemperature < + 70C at the ou ter ring

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    Dependance of RelubricationIntervals on Tempearture

    100

    85

    70

    55

    40

    Lubrication intervalC

    Temperature at the outer ring

    labov e 70C th e fac to r 0,5 appl ies

    fo r eac h t emperatu re r is e of 15C

    i.e. with a temperature ris e from e.g.

    70C u p to 85C the serv ic e l if e o fthe grease is cut by half .

    lb elow 70C the fac to r 2 app lies

    fo r eac h t emperatu re d ro p o f 15C

    i.e. wit h a temperature drop from e.g.70C down to 55 C the serv ic e li fe of th e

    grease is dou bled.

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    Lubrication by Oil

    is used at high speeds resp. at DN-factors exceeding1.000.000 and in case heat conduction is necessary.

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    Oil bath lubrication

    Suitable only for bearings with low speeds.

    During stand-stills the oil level should notquite reach the middle of the rolling element

    at the bottom. .

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    Oil injection lubrication

    At high speed it becomes necessary,

    that the air turbulence circulating with

    the bearing is penetrated by the oil.

    This is ensured by injecting oil under

    high pressure (min.15 m/s) from the side

    into the bearing.

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    Circulatory oil lubrication

    With increasing speed the service temperaturerises and accelerates the ageing of the

    lubricating oil.

    By circulatory lubrication the

    oil can be cooled and consequently

    the service temperature be reduced.

    Cooling

    pump

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    Lubrication with Solid Lubricants

    Deep groove ball bearings with increased clearance

    required at:

    lhigh temperatu res > + 200 C

    lhigh temperature var iat ions

    llow speed

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    Lubrication with Solid Lubricants -Exsample

    Lubr icat ion by Sol id

    Lub r icants only

    at temperatures > + 200 COKS 230 MoS2-High Temperatur e Paste(for thin-f ilm lub ricat ion durin g assembly and maintenance)

    in connection with

    OKS 310 MoS2-High -Temperatur e Lubric ant(for relubricat ion d uring o peration)

    The carrying fluid evaporates residue-free above 200C and

    dry MoS2 films remain, which assure lubrication up to 450C.

    Kiln-car bearings in the ceramics and brick industry

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    OKS Speciality Lubricants forRoller Bearings at:

    lHigh loads

    lShock stress

    l

    VibrationslLow or high speed

    lStop-and-go operation

    lVery low or very high temperatures

    lTemperature variations

    lHumid conditions

    lCorrosive influences

    lLong-term lubricating needs

    lUse in the food industry

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    Thank You

    for Your

    Attention

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